The field of the present invention is the art of U-bolt saddle clamps employed for example in the exhaust systems of automobiles and trucks powered by internal combustion engines.
The prior art directly concerned with such clamps is for the most part derived from a basic assembly comprising a U-bolt having a semicircular bight portion integrally connecting a pair of parallel legs which mount in axially slidable relation a sheet steel saddle member including tubular portions receiving and housing the bolt legs and connected by a central web extending transversely between the tubular housings integral therewith. The saddle has a work engaging edge facing and curved on the radius of the U-bolt bight. The free end portions of the bolt legs are threaded for reception of securing nuts that are drawn up against lock washers interposed between the nuts and adjacent ends of the tubular housings to advance the saddle and clamp together a coupling of telescoped cylindrical tubes disposed between the bight of the U-bolt and the curved edge of the saddle member.
Typical examples of prior art clamp structures most closely approaching the present invention are U.S. Pat. No. 2,719,345 to W. F. Riker and U.S. Pat. No. 3,137,053 to N. J. Osborn et al. Clamps of the types illustrated in these patents and in aforesaid U.S. Pat. No. 3,772,745 to William E. Dowling et al and 3,955,250 to Heckethorn have saddles formed from initially planar oblong blanks of relatively thin sheet steel. These are cut, stamped, and rolled or otherwise formed to provide a central web integrally connecting a pair of tubular portions arranged to slide axially on the legs of an associated U-bolt. In some cases the saddle web is only a single sheet; in others, such as Heckethorn, the web is constituted of a pair of identical sheets joined in parallel in full face contact relation or in laterally spaced relation with or without an identical intermediate spacer sheet.
In all cases the work engaging edge of the saddle web is required to impart sufficient clamping pressure to indent a semicircular bead in both the inner and outer sections of a telescoped tubular conduit coupling to which the clamp is applied. The applied clamping pressure is a function of the torque level to which the securing nuts are finally tightened when they are drawn up on the threaded ends of the U-bolt legs. Tests have clearly shown that in clamps of the foregoing general types, the saddle webs which have no longitudinal reinforcement usually start to twist laterally and roll over when tightened to torque levels in the vicinity of 16 foot lbs. Clamp saddles longitudinally reinforced in the manner disclosed in aforesaid Dowling et al U.S. Pat. No. 3,772,745 successfully resist such twisting and rolling at much higher torque levels, such as 40 foot lbs. However, in the present stage of the automotive industry, there is an increasing demand for clamps having a much greater clamping ability, especially those designed to meet certain critical requirements in connection with anti-pollution catalytic devices on new vehicles, which must withstand torque levels of 50 foot lbs. and higher. The Heckethorn clamp as noted in U.S. Pat. No. 3,955,250 was designed to meet these requirements.
While the aforesaid Heckethorn patent meets all strength requirements, there still exists a need for a clamp of somewhat lesser strength for lighter duty usage which will still withstand relatively high compressive or tensile stresses, yet do so at a lower cost per clamp and be of lighter weight.